The invention relates to a cordless (i.e, battery-operated) device such as a power tool or kitchen appliance. More particularly, the present invention relates to a battery pack and receptacle for mounting the pack in the device.
For the consumer market, most cordless devices have a battery pack made integrally in the device housing because of reduced cost, increased end user convenience and sturdiness. However, because of the desire to provide consumer devices with detachable packs simplifying the recycling of the packs and the desire to provide a family of cordless devices using an interchangeable pack and a single charger, there is strong commercial interest in developing a sturdy, convenient, low cost, compact and easily automated battery pack. Of course, these design goals are not unique to consumer devices but also are equally desirable for professional cordless devices in which detachable packs have been the standard for many years.
Accordingly, a primary object of the present invention is to provide an improved battery pack and receptacle for mounting the pack in a cordless device embodying the foregoing design objectives.
In accordance with one aspect of the invention, a battery pack comprises an elongated cylindrical casing with a longitudinal axis of symmetry, a plurality of cells in the casing and first and second pack terminals having opposite polarities, coaxial with the casing axis and located adjacent to the casing forward end. The pack terminals are electrically connectable in a cordless device regardless of the angular orientation of the pack about the casing axis. Such a pack provides greater end user convenience.
Preferably the casing is metal, is electrically connected to a first cell terminal of a rear cell in the pack and constitutes the first pack terminal. The second pack terminal is preferably a top disposed across the casing forward end. To provide shielding for the pack terminals, the top preferably defines a cavity in the casing forward end and has a forwardly projecting nipple fully recessed within the casing cavity.
Alternatively, the second pack terminal may be formed by a button terminal of a forward cell exposed at the casing forward end.
Alternatively, the second pack terminal may be formed by a shielded female barrel-shaped terminal fully recessed within the casing cavity.
To provide a pack with multiple output voltages, a third pack terminal may be located in the casing cavity coaxially of the casing axis, have a polarity the same as the second pack terminal and be electrically connected to a first cell terminal of a forward cell in the pack thereby electrically by passing the forward cell.
In accordance with a second aspect of the invention, a battery pack comprises a tubular metal casing, a metal base cap closing the rear end, and a fixed abutment formed in and closing the casing forward end. A plurality of electrically connected, mechanically disconnected cells are disposed end to end in the casing. The metal base cap is electrically connected to and mechanically disconnected from an adjacent rear cell and forms with the casing a first pack terminal. A second pack terminal is located at the casing forward and is electrically connected to an adjacent forward cell. A spring engages one of the cells and biases the cells tightly together in compression to form good electrical contact between adjacent cells and pack terminals to permit high current discharge rates. Such a pack has no welded connections and is, therefore, more reliable and lower in cost.
The abutment preferably is a lip formed at the forward end of the casing to terminate the casing and retain the cells and pack terminals in compression. To provide a pack with multiple output voltages, a third pack terminal is preferably compressed between the casing lip and a forward cell. The third terminal may be formed as a sleeve having (a) axial fingers engaging the forward cell can and (b) transverse fingers overlapping and helping to secure the top.
Alternatively, the abutment may be formed by an annular bead formed in the casing slightly forwardly of the forward cell.
The second pack terminal is preferably a metal top closing the casing forward end electrically connected to and mechanically disconnected from a button terminal of the forward cell. Alternatively, the second pack terminal may be constituted by the button terminal of the forward cell exposed at the casing forward end. Alternatively, the second pack terminal may be formed by a shielded female barrel-shaped terminal fully recessed within the casing cavity.
The spring is preferably formed integrally in the base cap but may also be a separate component.
In accordance with a third aspect of the invention, battery packs in accordance with either the first or the second aspect of the invention described above may include an integral plastic plug containing the second and third pack terminals separated by an insulating wall. The second terminal is preferably a tubular nipple filled with plastic and further preferably covered by a plastic projection extending forwardly from the forward end of the nipple.
In accordance with a fourth aspect of the invention, a cordless device comprises a cavity, a receptacle in the cavity and a battery pack in accordance with either the first, second or third aspect of the invention described above. The pack is electrically connectable in the receptacle regardless of the angular orientation of the pack about the casing axis.
The receptacle preferably comprises a housing defining a cavity having a longitudinal axis coaxial to the casing axis when the pack is mounted in the receptacle. The receptacle further includes an appropriate number of receptacle terminals for mating with a pack having either two or three pack terminals.
The receptacle terminals are preferably coaxially located about the receptacle cavity axis.